some ideas.... maybe for a test only... we could send trim commands on raid1 arrays only or 'raid0 linear' since they don´t stripe, this could be 'easy' to develop when filesystem send trim, we send it to down device (/dev/sdX99) there´s a problem of offset (for raid1) maybe some devices just work with 4096bytes blocks on trim command, maybe not we could implement and put in a beta/alpha realease to test like ext4 guys are doing with discard command (it´s a user option today) 2011/6/29 Scott E. Armitage <launchpad@xxxxxxxxxxxxxxxxxxx>: > On Wed, Jun 29, 2011 at 7:10 AM, Tom De Mulder <tdm27@xxxxxxxxx> wrote: >> However, that might not necessarily be a problem; tools exist that can be run manually (slightly fsck-like) and tell the drive which blocks can be erased. > > For RAID5/6 at least, md will still require knowledge of what stripes > are and are not in use by the filesystem. In the current > implementation, the entire array must be consistent, regardless of > whether or not a particular block is in use. As far as my > understanding goes, any level of TRIM support for parity arrays would > be a fundamental shift in the way md treats the array. > > The simplest solution I see is to do as Niel suggested, and mimic TRIM > support at the RAID level, and pass commands down as necessary. An > alternative solution would be to add a second TRIM layer, where md > maintains a list of what is or is not in use, and once an entire > stripe has been discarded by the filesystem, it can send a single TRIM > command to each member drive to drop the entire stripe contents. This > adds abstraction for the filesystem layer, allowing it to treat the > RAID array like a regular SSD, but adds significant complexity to md > itself. > > -Scott > > p.s. Sorry if you receive this twice; Majordomo rejected the first one > on HTML subpart basis. > > -- > Scott Armitage, B.A.Sc., M.A.Sc. candidate > Space Flight Laboratory > University of Toronto Institute for Aerospace Studies > 4925 Dufferin Street, Toronto, Ontario, Canada, M3H 5T6 > -- > To unsubscribe from this list: send the line "unsubscribe linux-raid" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- Roberto Spadim Spadim Technology / SPAEmpresarial -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
